This invention relates to intrusion detection systems of the type which use taut wires to form a physical barrier, and which use tension sensors coupled to the taut wires to detect attempts to defeat the physical barrier.
A variety of intrusion detection systems are known, ranging from those protecting private residences to those protecting large-scale, relatively high security, facilities such as airports and military installations. A number of the systems of the second kind, those protecting large-scale facilities, typically provide a combination of a physical barrier and an electronic detection capability. A taut wire intrusion detection system provides such a combination. Such a system is available, for example, from Safeguards Technology of Hackensack, N.J.
A typical taut wire intrusion detection system will include sensors, sensor posts, taut wires, anchor posts, and slider posts. A single or several sensors will usually be mounted on a post, typically referred to as the xe2x80x9csensor post.xe2x80x9d Taut wires, commonly formed from a double strand steel barbed wire, are attached to the single sensor or group of sensors mounted on the sensor post. Each taut wire segment usually terminates at two anchor posts placed on opposite sides of the sensor post to form a subsection of the intrusion detection system. Spiral shaped steel rods typically referred to as xe2x80x9cslider posts,xe2x80x9d are sometimes placed vertically between the taut wires as to prevent the wires from bowing or sinking down. Each taut wire is maintained in tension between the anchor posts such that the sensor will detect a cut or deflection of the taut wire, triggering an alarm at a control center. Multiple subsections constructed in this manner are linked together to secure a given area.
The threshold distance taut wire segments are required to be displaced (displacement requirement) in a typical taut wire system, whereby the sensor or sensors of the sector can detect an intrusion attempt, varies along the length of the sector such that certain areas of the taut wire fence are more vulnerable to intrusion attempts than others. The level of force (force requirement) that must be applied to the taut wire segments to trigger an alarm condition also varies along the length of the sector because the anchor post is an anchoring element that is not sensitive to intrusion attempts. Combined together, the displacement requirement and the force requirement can be perceived as the sensitivity of the taut wire system, such that the sensitivity level is inversely proportional to both requirements. The method and system of the present invention provide an increased uniformity of sensitivity for taut wire intrusion detection systems.
The method of the present invention results in a lower sensitivity variance in a section of the system by using supporting posts that include both sensor and anchor elements. The supporting posts are arranged such that each post contains both sensor and anchor elements. The sensitivity can be made to have a very low variance by adapting the arrangement of sensors and anchor elements to the particular variance exhibited by the taut wire segments of the system.
The present method provides a more reliable system which has uniform sensitivity over the secured sections. The present invention allows for a more precise identification of an intrusion location by eliminating the sector method of constructing intrusion detection systems. The method of the present invention employs a section paradigm as opposed to a sector paradigm since each portion of a system of the present invention includes a variable number of posts.
The present invention also provides a taut wire intrusion detection system that has a first support post which includes at least one taut wire anchor element and at least one taut wire sensor. The system has a second support post which includes at least one taut wire anchor element and at least one taut wire sensor. A first taut wire segment extends under tension between the first and second support posts. The first taut wire segment is anchored to the first supporting post by an anchor element and is coupled to a taut wire sensor of the second support post. A second taut wire segment extends under tension between the first and second support posts such that the first and second taut wire segments are vertically separated from one another. The second taut wire segment is anchored to the second supporting post by an anchor element and is coupled to a taut wire sensor of the first support post.
The present invention additionally provides for an increase in the accuracy of identifying the intrusion location when an alarm condition is sensed by the sensors on the supporting posts. The present invention additionally eliminates the need to use special anchoring elements to account for the weaknesses of a system near the anchor posts.